After the LaserWriter gets the image of the page in memory, the PostScript command "showpage" is called to print the page. The "showpage" command looks up the value in "#copies" to determine how many copies to print and then prints that number of pages. Once the printing is completed, the "showpage" command does the equivalent of the "erasepage" and "initgraphics" PostScript commands.
The "erasepage" command erases the entire image in the LaserWriter memory by painting it with gray level 1, which is normally white. The "initgraphics" command resets many of the graphics states to their default values.
For more information on "showpage", "erasepage", and "initgraphics", see pages 238, 161, and 184, respectively, of the "PostScript Language Reference Manual."